The purpose of the supplemental program application is to increase the scope of National HIV Behavioral Surveillance (NHBS) in Chicago to include surveillance of young men between 13 and 17 years of age who have sex with men (YMSM) as a component within an on- going surveillance system operated and maintained by the Chicago Department of Public Health STI/HIV Division. This behavioral surveillance system will ascertain the prevalence of and trends in HIV risk behaviors and among this group of YMSM, and measure the prevalence of HIV infection. Information from the system will be used to develop and contribute to the evaluation of national and local HIV prevention services and programs. This announcement provides an opportunity to capitalize on existing capacity in NHBS in Chicago. Since 2003, Chicago NHBS has been successful at recruiting at-risk individuals from non-health care community settings using scientifically sound methodologies to maintain an ongoing system for citywide surveillance of behaviors and HIV infection. In Chicago, 47% of MSM diagnosed with HIV in 2009 were between 13 and 29 years old. Since 2000, MSM less than 19 years of age have gone from 2% of all MSM HIV diagnoses to 7% of all MSM HIV diagnoses. (Chicago Department of Public Health. STI/HIV Surveillance Report, 2011. Chicago, IL: City of Chicago; November, 2011.) Data such as this show the need to increase prevention and research activities among the young YMSM population. While the NHBS system is already set up and operating in Chicago to monitor behavioral trends among MSM over the age of 18, this supplemental project offers the opportunity to include YMSM between 13 and 17 years of age. The objectives of this project will be achieved in Chicago by conducting formative research, community-based surveys, and HIV testing among YMSM ages 13-17. In addition, risk behaviors and HIV prevalence among YMSM ages 13-17 will be assessed. Access to and utilization of HIV prevention programs also will be measured. This project will be a formal collaboration between the Chicago Department of Public Health and local HIV prevention organizations, community-based organizations (CBOs), and academic institutions. A multi- method approach to sampling will be implemented. In total, 600 eligible YMSM will be recruited from Chicago. PUBLIC HEALTH RELEVANCE: This proposed behavioral surveillance system will ascertain the prevalence of and trends in HIV risk behaviors and among this group of YMSM, and measure the prevalence of HIV infection. Monitoring behaviors that place people at risk for HIV infection is a key element of an integrated surveillance system and behavioral data, specifically, are essential for designing and evaluating prevention interventions for groups at high risk for acquiring HIV infection.